Serogroup B and C strains of Neisseria meningitidis (Nm) together account for the majority of invasive diseases in Europe and the United States. Vaccines against individual Nm serogroups are presently available. The NIPH (National Institute of Public Health of Norway) NmB vaccine is safe, elicits strain-specific immunity in children and adults, and is efficacious in preventing NmB disease in adolescents. This vaccine has been typically combined with meningococcal C polysaccharide vaccine and given with alum. The plain polysaccharide vaccine component, however, is not effective in infants and young children. The Chiron NmC conjugate (conj.) vaccine is also safe, elicits high titers of serum bactericidal antibody in infants vaccinated as young as two and three months of age, and induces immunologic B cell memory to the unconjugated NmC polysaccharide. Since both serogroups cause disease, a combination vaccine which induces an immune response to both serogroups would be highly advantageous.